Chapter 9

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What is the difference between fermentation and cellular respiration.

Fermentation- catabolic process that makes a limited amt. of ATP from glucose w/o an electron transport chain and that produces a characteristic end product,such as alcohol or lactic acid w/o the use of oxygen.

Cell resp.- catabolic pathways of aerobic and anaerobic respiration, which break down organic molecules for the production of ATP; oxygen in consumed as a reactant along with the organic fuel.

Give the formula with names for the catabolic degradation of glucose by cellular respiration.

C6H12O6 + 6 O2 ------> 6 CO2 + 6 H2O + Energy (ATP and Heat)

Glucose; oxygen; carbon dioxide; water

Both cellular respiration and photosynthesis are ____. In __, reactions pay attention to the flow of ____.

redox reactions

redox

electrons

What is the difference between oxidation and reduction?

Oxidation- loss of electrons from a substance involved in a redox reaction.

Reduction- gain or addition of electrons to a substance involved in a redox reaction

The following is a generalized formula for a redox reaction:
Xe- + Y --> X + Ye-What is the reducing agent? Oxidizing agent?
What becomes oxidized? reduced?

In cell respiration, ___ are not transferred directly from __ to ___. Each electron is coupled with a __ to form a __ atom. The hydrogens are held in the cell temporarily by what electron carrier?

electrons

glucose

oxygen

proton

hydrogen

NAD+, a coenzyme

A derivative of the B vitamin niacin; coenzyme that functions as an oxidizing agent during respiration when it acts as an electron acceptor

NAD+

an organic molecule serving as an enzyme such as a vitamin

coenzyme

What is the function of the electron transport chain in cell respiration?

breaks the fall of electrons to oxygen into several energ- releasing steps.

Show the normal downhill route most eletrons follow in cellular respiration.

glucose --> NADH --> electron transport chain --> oxygen

Why is glycolysis an appropriate term for this step of cell resp?

It means, sugar splitting, which is exactly what happens. Glucose, a six- carbon sugar, is broken into two three- carbon sugars.

The starting product of glycolysis is teh six- carbon sugar ____, and the ending product is two ___ carbon compounds termed ___.

glucose

three

pyruvate

The ten individual steps of glycolysis can be divided into two stages: ___ and ____.

energy investment

energy pay-off

In glycolysis, ATP is formed in which phase?
How much?
What is the net gain?
Why?

energy payoff

4

2

Because in the energy- investment phase, two ATP are used up.

After glycolysis, most of the energy is still present in the two molecules of ___.

pyruvate

Glycolysis occurs in the ___ of the cell.

cytoplasm (cytosol)

WHat is the relationship between glycolysis and oxygen?

Glycolysis can occur whether or not oxygen is present. If oxygen is present, the chemical energy stored in pyruvate and NADH can be extracted by the cirtic acid cycle and oxidative phosphorylation.

To enter the ___, the ___ must enter the mitochondria by ___. These things are necessary to convert ___ to ___.

citric acid cycle

pyruvate

active transport

pyruvate acetyl CoA

Explain the three steps in the conversion process of pyruvate to acetyl CoA.

1) Pyruvate's carboxyl group (-COO-), which is already fully oxidized and thus has little chemical energy, is removed and given off as a molecule of CO2. (1st step in which CO2 is released during respiration.

2) The remaining two- carbon fragment is oxidized, forming a compound named acetate (the ionized form of acetic acid). An enzyme transfers extracted electrons to NAD+, storing energy in the form of NADH.

3) Finally, CoA, a sulfur- containg compound derived from a B vitamin, is attached to the acetate by an unstable bond that makes the acetyl group very reactive.

Because of the chemical nature of the CoA group, the product of this chemical grooming (transferring pyruvate to
acetyl CoA), ___ has a high potential energy. (The reaction of ___ to yield lower energy products is highly ___. This molecule is now ready to feed its acetyl group, into the ___ for further oxidation.

acetyl CoA

acetyl CoA

exergonic

citric acid cycle

How many times does the citric acid cycle occur for each molecule of glucose?

twice

In the citric acid cycle, for each turn, how many... are formed?
NADH?
FADH2?
ATP?

3

1

1

In the citric acid cycle, how may total carbns are lost as pyruvate is oxidized?
The carbons have been lost in the molecule ___.

2

carbon dioxide

Altogether, how many... are formed in the citric acid cycle?
NADH?
FADH2?
ATP?

6

2

2

The step that converts pyruvate to acetyl COA at the top of the diagram also occurs twice per glucose. This step accounts for two additional reduced ___ molecules and two carbon dioxide molecules.

NADH

Explain what has happened to the six- carbon molecules found in the original glucose molecule.

They have been released as CO2. Only 2 ATP molecules have been produced. The energy is held in the electrons in the electron carriers NADH and FADH2.

Oxidative phosphorylation involves two components: ___ and ___.

electron transport chain

ATP synthesis

In the electron transport chain, the molecule at zero free energy, which is ___, is lowest of all the molecules in free energy and highest in eectronegativity.

oxygen

Why is oxygen the ultimate acceptor?

It is very electronegative. When it's not available, the transport of electrons comes to a halt. No hydrogen ions are pumped and no ATP is produced.

Oxygen stabilizes the electrons by combining with two hydrogen ions to form what compound?

water

The two electron carrier molecules that feed electrons into the electron transport system are __ and __.

NADH

FADH2

Explain the overall concept of how ATP synthase uses the flow of hydrogen ions to produce ATP.

1. H+ ions flowing down their gradient enter a 1/2 channel in a stator, which is anchored in the membrane.

2. H+ ions enter binding sites w/in a rotor, changing the shape of each subunity so that the rotor spins within the membrane

3. Each H+ ion makes one complete turn before leaving the rotor and passing through a second 1/2 channel in the stator into the mitochondrial matrix.

4. Spinning of the rotor causes an internal rod to spin as well. This rod extends like a stalk- into the knob below it, which is held stationary by part of the rotor.

5. Turning of the rod activates catalytic sites in the know that produce ATP from ADP and Pi

What is the role of the electron transport chain in forming the H+ gradient across the inner mitochondrial membrane?

The chain is an energy converter that uses the exergonic flow of electrons from NADH to FADH2 to pump H+ across the membranes from the mitochondrial matrix to the intermembrane space. The H+ has a tendency to move back across the membrane, diffusing own its gradient. And the ATP synthases are the only sites that provide a route through the membrane for H+.

What is the major function of the electron transport chain?

forming the H+ gradient across the inner mitochondrial membrane

__ is an energy coupling mechanism that uses energy stored in the form of hydrogen ion gradient across a membrane to drive cellular work, such as ATP synthesis. Most ATP synthesis occurs by this.

chemiosmosis

__ is the potential energystored in the form of an electrochemical gradient, generated by the pumping of hydrogen ions across a biological membrane during chemiosmosis.

Pyruvate is reduced directly by NADH to form lactate as an end product with no rlease of CO2.

- When pyruvate is reduced by NADH, NAD+ is formed in the process and lactate is formed as a waste product.

Stress how NAD+ is recycle in lactic acid and alcohol fermentation.

Pyruvate serves as an electron acceptor for oxidizing NADH back to NAD+.

Why is pyruvate is a key juncture in metabolism?

It represents a fork in the catabolic pathways of glucose oxidation. In a facultative anaerobe, which is capable of bothaerobic cell respiration and fermentation, pyruvate is committed to one of those two pathways, usually of depending on whether or not oxygen is present

What three organic macromolecules are often utilized to make ATP by cellular respiration?

proteins, fats, sucrose, glucose, sucrose (carbohydrates)

Explain the difference in energy usage between the catabolic reactions of cellular respiration and anabolic pathways of biosynthesis.